Load carrier with mode changer

ABSTRACT

A multi-mode load carrier is convertible to assume a storage mode, a cart mode, and a hand-truck mode. The load carrier includes a rolling base and a base pusher having a handgrip.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.14/330,890, filed Jul. 14, 2014, which claims priority to U.S.Provisional Application Ser. No. 61/845,648, filed Jul. 12, 2013, whichis expressly incorporated by reference herein.

BACKGROUND

The present disclosure relates to a load carrier and particularly to aload carrier with wheels that can be collapsed to assume a compactstorage mode. More particularly, the present disclosure relates to awheeled load carrier that can be reconfigured in the field by a user tofunction in two operating modes.

SUMMARY

According to the present disclosure, a collapsible load carrier includesa rolling base and a base pusher mounted on the rolling base formovement relative to the rolling base. In illustrative embodiments, thecollapsible load carrier further includes a load-carrier mode changercoupled to the rolling base and to the base pusher. The mode changer isconfigured to pivot left and right front wheel units of the rolling baserelative to companion wheel-support rails of the rolling base from afolded storage position to an unfolded rolling position.

In illustrative embodiments, the rolling base comprises a load-supportframe including left and right wheel-support rails and the base pusheris mounted on the rails for pivotable movement relative to theload-support frame about a base-pusher pivot axis. The rolling base alsoincludes a left front wheel unit mounted on the left wheel-support railfor pivotable movement between a folded storage position and an unfoldedrolling position and a right front wheel unit mounted on the rightwheel-support rail for pivotable movement between a folded storageposition and an unfolded rolling position. The mode changer is coupledat a rear end to the pivotable base pusher and at a front end to thepivotable left and right front wheel units.

In illustrative embodiments, the load-carrier mode changer is coupled tothe rolling base and to the base pusher and configured to provide meansfor converting the load carrier either to a flat storage mode, afront-and-rear-wheel cart mode, or a 2-wheel hand-truck mode at theoption of a user without tools. The mode changer includes a frontlinkage coupled to the front wheel units and arranged to slide on thewheel-support rails of the load-support frame. The mode changer alsoincludes a rear linkage coupled to the pivotable base pusher and to thefront linkage in either a FIRST POSITION or a SECOND POSITION selectedby the user. It is within the scope of the present disclosure to use asingle rear wheel so that three wheels engage and roll on groundunderlying the rolling base in an alternative front-and-rear-wheel cartmode of the load carrier.

In illustrative embodiments, the rolling base includes two front wheelsand the base pusher includes two rear wheels. All four wheels aredisengaged from ground underlying the rolling base when the load carrieris in the flat storage mode. All four wheels are arranged to engage androll on ground underlying the rolling base when the load carrier isconfigured in the field by a user to assume a front-and-rear wheel cartmode. In contrast, only the two front wheels are arranged to engage androll on the ground underlying the rolling base when the load carrier isconfigured in the field by the user to assume a 2-wheel hand-truck mode.

In illustrative embodiments, the base pusher can be pivoted by a userabout the base-pusher pivot axis through a 180° angle to move relativeto the rolling base from a stored position on top of the load-supportframe of the rolling base to change the load carrier from a flat storagemode to a 2-wheel hand-truck mode. First the base pusher is pivoted in arearward first direction through about a 90° angle to assume an uprightcart position to place the rear wheel(s) on the ground while the rearlinkage is in the FIRST POSITION on the front linkage to cause the frontand rear linkages to move together as a unit to pivot the left and rightfront wheel units to the unfolded rolling positions and to place thefront wheels on the ground along with the rear wheel(s) to establish thefront-and-rear-wheel cart mode of the load carrier. Then the base pusheris pivoted in the same direction through another 90° angle to disengagethe rear wheel(s) from the ground during movement of the rear linkage tothe SECOND POSITION on the front linkage to place the base pusher inline with the top of the load-support frame of the rolling base toassume a laidback hand-truck position to establish the 2-wheelhand-truck mode of the load carrier. Thus, the load carrier can beconverted in the field by a user without tools using the load-carriermode changer to assume either a flat storage mode, afront-and-rear-wheel cart mode, or a 2-wheel hand-truck mode.

Additional features of the present disclosure will become apparent tothose skilled in the art upon consideration of illustrative embodimentsexemplifying the best mode of carrying out the disclosure as presentlyperceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1A is a perspective view of a collapsible load carrier in a compactflat storage mode showing that a pivotable base pusher has been pivotedabout a base-pusher pivot axis to lie in a stored position on top of arolling base and showing that two front wheels in the rolling base liein folded storage positions under the U-shaped handgrip of the basepusher and two rear wheels included in the base pusher are arranged tolie above ground underlying the rolling base and suggesting that theload carrier also includes a load-carrier mode changer that is coupledto the pivotable base pusher and to the front wheels and can be operatedby a user in the field in a manner suggested diagrammatically in FIGS.4A-4D and illustratively in FIGS. 5-7 and 12-14 to convert the loadcarrier from a flat storage mode shown in FIG. 1A to afront-and-rear-wheel cart mode shown in FIG. 1B and to a 2-wheelhand-truck mode shown in FIG. 1C;

FIG. 1B is a perspective view of the load carrier of FIG. 1A after ithas been reconfigured in the field by a user using the load-carrier modechanger to assume a front-and-rear-wheel cart mode in which the loadcarrier can roll on its two front wheels and two rear wheels by pivotingthe base pusher about the base-pusher pivot axis upwardly away from therolling base through an angle of about 90° to assume an upright cartposition to cause forward sliding movement of the load-carrier modechanger on two horizontal rails included in a load-support frame of therolling base to engage and pivot each of the front wheel units outwardlyfrom the folded storage positions shown in FIG. 1A to the unfoldedrolling positions shown in FIG. 1B and suggesting that the mode changerincludes a front linkage coupled to the left and right front wheel unitsand a rear linkage coupled to the front linkage and to the pivotablebase pusher;

FIG. 1C is a perspective view of the load carrier of FIGS. 1A and 1Bafter it has been reconfigured in the field using the load-carrier modechanger to assume a 2-wheel upright hand-truck mode in which the loadcarrier can roll only on its two front wheels by moving a pivotablepusher rotator included in the rear linkage of the load-carrier modechanger in a forward direction on a slidable spreader driver included inthe front linkage of the load-carrier mode changer toward thelarger-diameter front wheels from a first position to a second positionto pivot the base pusher rearwardly about the base-pusher pivot axisfrom the upright cart position through an angle of about 90° to assume alaidback hand-truck position and suggesting that the front linkageincludes a spreader driver and a wheel spreader and that the rearlinkage includes a pivotable pusher rotator and a push rod;

FIG. 2 is an exploded perspective view of components comprising thecollapsible load carrier of FIGS. 1A-1C;

FIG. 3 is a view similar to FIG. 2 showing several load carriersubassemblies and, in particular, showing (1) a rolling base includingleft and right front-wheel support rails and left and right front wheelunits having large-diameter front wheels and being formed to be mountedon forward ends of the front-wheel support rails for pivotable movementbetween folded storage positions lying in a single horizontal plane whenthe load carrier is in the compact flat storage mode as shown in FIG. 1Aand unfolded rolling positions lying in spaced-apart parallel verticalplanes when the load carrier is in the front-and-rear-wheel cart modeshown in FIG. 1B and the 2-wheel hand-truck mode shown in FIG. 1C; (2) abase pusher having small-diameter rear wheels; and (3) a load-carriermode changer comprising a front linkage adapted to be coupled to theleft and right front wheel units and formed to be mounted forback-and-forth sliding movement on the front-wheel support rails and arear linkage adapted to be coupled to the front linkage and to thepivotable base pusher and to cooperate with the front linkage to causethe front wheel units to pivot between unfolded storage positions andfolded rolling positions in response to pivoting movement of the basepusher about the base-pusher pivot axis from the stored position shownin FIG. 1A to the upright cart position shown in FIG. 1B;

FIGS. 4A-4C are diagrammatic views showing sliding movement of theload-carrier mode changer on the left and right rails of the rollingbase to cause the front wheel units to pivot from the folded storagepositions to the unfolded rolling positions in response to pivotingmovement of the base pusher from the stored position to the upright cartposition and FIG. 4D is a diagrammatic view showing sliding movement ofthe pivotable pusher rotator included in the rear linkage of theload-carrier mode changer on a slidable spreader driver included in thefront linkage of the load-carrier mode changer to cause the base pusherto pivot from the upright cart position suggested in FIG. 4C to thelaidback hand-truck position suggested in FIG. 4D;

FIG. 4A is a diagrammatic view of the load carrier in the compact flatstorage mode of FIG. 1A and showing that the front linkage of theload-carrier mode changer includes a slidable spreader driver coupled tothe pivotable base pusher via the rear linkage and mounted for slidingmovement on the rails included in the rolling base and a wheel spreaderarranged to interconnect the slidable spreader driver and the pivotableleft and right front wheel units and showing that the wheel spreader isarranged to engage a ROOT section of each front wheel unit andsuggesting that the pivotable base-pusher rotator included in the rearlinkage of the load-carrier mode changer is coupled to the base pusherand mounted for pivoting movement on the slidable spreader driver andarranged to lie in a FIRST POSITION on the slidable spreader driver;

FIG. 4B is a diagrammatic view similar to FIG. 4A showing that the leftand right front wheel units have pivoted toward one another through anangle of about 45° owing to engagement of the wheel spreader with theCAM section of each front wheel unit in response to pivoting movement ofthe base pusher away from the rolling base about the base-pusher pivotaxis to cause sliding movement of the slidable spreader driver on theleft and right rails of the rolling base in a direction toward the frontwheel units and movement of the wheel spreader on the CAM section ofeach front wheel unit;

FIG. 4C is a diagrammatic view similar to FIGS. 4A and 4B showing thatthe front wheel units have been pivoted further on the rails to assumethe unfolded rolling positions in response to pivoting movement of thebase pusher to assume the upright cart position and suggesting that thewheel spreader has been moved along the CAM section of each front wheelunit to engage the LOCK section of each front wheel unit to retain thefront wheel units in the unfolded rolling positions;

FIG. 4D is a diagrammatic view similar to FIGS. 4A-4C showing that thebase pusher has been pivoted in a rearward direction about thebase-pusher pivot axis relative to the rolling base to assume a laidbackhand-truck position in response to pivoting movement of the pivotablebase-pusher rotator on the slidable spreader driver from the FIRSTPOSITION in a direction away from the base-pusher pivot axis and towardthe front wheels to arrive at a SECOND POSITION;

FIG. 5 is a perspective view of an illustrative collapsible load carrierin the flat storage mode shown diagrammatically in FIG. 4A and showingthe base pusher in the stored position on top of a load-support frame ofthe rolling base and the left and right front wheel units in theirfolded storage positions under a U-shaped handgrip included in the basepusher;

FIG. 5A is a reduced-size side elevation view of the load carrier ofFIG. 5;

FIG. 6 is a perspective view of an illustrative collapsible load carrierin the transition mode shown diagrammatically in FIG. 4B showingpivoting movement of the left and right front wheel units to reach amidway point between the folded storage positions shown in FIG. 5 andthe unfolded rolling positions shown in FIGS. 7 and 8;

FIG. 6A is a reduced-size side elevation view of the load carrier ofFIG. 6;

FIG. 7 is a perspective view of an illustrative load carrier in thefront-and-rear wheel cart mode shown diagrammatically in FIG. 4C inwhich both front wheels and both rear wheels roll along the groundunderlying the load carrier and showing the base pusher in the uprightcart position and the left and right front wheel units in their unfoldedrolling positions;

FIG. 7A is a reduced-size side elevation view of the load carrier ofFIG. 7;

FIG. 8 is a detail perspective view of a portion of the load carrier ofFIG. 7 broken away to show that the spreader driver retainer includes apair of slider-retainer pins coupled to the load-support frame that holdthe slidable spreader driver in place along the load-support frame whenthe base pusher reaches the upright cart position and a pin releasecoupled to the slidable spreader driver for pushing the slider-retainerpins out of engagement with the slidable spreader driver when the basepusher is collapsed from the upright cart position to the storedposition;

FIG. 8A is a detailed top plan view of a portion of FIG. 8 showing thatthe slider-retainer pins are received in apertures formed in theslidable spreader driver to hold the slidable spreader driver in placerelative to the load-support frame;

FIG. 9 is a view similar to FIG. 8 showing a user pressing aslider-release button included in the pin release of the spreader driverretainer so that the slidable spreader driver is free to move relativeto the load-support frame when the base pusher is collapsed from theupright cart position to the stored position;

FIG. 9A is a detailed top plan view of a portion of FIG. 9 showing thatthe pin release includes pin pushers that push the slider-retainer pinsout of the apertures formed in the slidable spreader driver when theslider-release button is pressed by a user;

FIG. 10 is an enlarged partial perspective view of a portion of the loadcarrier of FIG. 6 showing engagement of the wheel spreader of theload-carrier mode changer on the CAM section of the right front wheelunit of the rolling base;

FIG. 11 is an enlarged partial perspective view of a portion of the loadcarrier of FIG. 7 showing engagement of the wheel spreader of theload-carrier mode changer in the LOCK (channel) section of the rightfront wheel unit of the rolling base and showing an angled second leg ofthe CAM section of the right front wheel unit that extends between avertical first leg of the CAM section and the LOCK (channel) section;

FIGS. 12-14 show conversion of the load carrier of FIG. 7 from thefront-and-rear-wheel cart mode to the 2-wheel hand-truck mode;

FIG. 12 is a perspective view of the load carrier of FIG. 7 after apivotable toe-plate shelf included in the rolling base and located abovethe front wheels has been pivoted in a forward direction from aninactive position shown in FIG. 7 to an active position shown in FIG.12;

FIG. 12A is a reduced-size side elevation view of the load carrier ofFIG. 12;

FIG. 13 is a perspective view of the load carrier of FIG. 12 in atransition mode showing rearward pivoting movement of the base pusherabout the base-pusher pivot axis to reach a midway point between theupright cart position shown in FIG. 12 and the laidback hand-truckposition shown in FIG. 14 in response to operation of the pivotablepusher rotator included in the rear linkage of the load-carrier modechanger;

FIG. 13A is a reduced-size side elevation view of the load carrier ofFIG. 13;

FIG. 14 is a perspective view of the load carrier of FIGS. 12 and 13 inthe 2-wheel hand-truck mode shown diagrammatically in FIG. 4D andshowing the left and right front wheel units in the unfolded rollingpositions, the base pusher in the laidback hand-truck position, and thepivotable pusher rotator of the rear linkage of the load-carrier modechanger in the SECOND POSITION on the slidable spreader driver of thefront linkage of the load-carrier mode changer;

FIG. 14A is a reduced-size elevation view of the load carrier of FIG.14;

FIG. 15 is a detail perspective view of the rear linkage included in theload carrier of FIG. 12 showing that the pusher rotator arranged to liein the FIRST POSITION in engagement with a first side of the slidablespreader driver to hold the slider links of the handgrip in place whenthe load carrier is in the cart mode until a user unlocks the spreaderdriver retainer so that the pusher links of the push rod can moverelative to the slidable spreader driver as shown in FIG. 16;

FIG. 16 is a view similar to FIG. 15 of the rear linkage included in theload carrier of FIG. 13 showing the spreader driver retainer disengagedfrom the slidable spreader driver and the slider links of the handgrippivoted relative to the slidable spreader driver as the base pushermoves from the upright cart position to the laidback hand-truck positionduring reconfiguration of the load carrier from the front-and-rear-wheelcart mode to the 2-wheel hand-truck mode;

FIG. 17 is a view similar to FIGS. 15 and 16 of the rear linkageincluded in the load carrier of FIG. 14 showing that the pusher rotatorarranged to lie in a SECOND POSITION in engagement with a second side ofthe slidable spreader driver, opposite the first side, to hold theslider links of the handgrip in place when the load carrier is in the2-wheel hand-truck mode;

FIG. 18 is a perspective view of another illustrative load carriersimilar to the load carrier shown in FIGS. 1-17 that includes analternative pusher rotator for maintaining the position of the rearlinkage thereby to hold the base pusher in either the upright cartposition or the laidback hand-truck position; and

FIG. 18A is a detail view of a portion of the load carrier of FIG. 18showing that the alternative pusher rotator includes a forward lock andan aft lock each coupled to the slidable spreader driver and adapted toengage a handle coupled to the rear linkage when the base pusher is inone of the upright cart position or the laidback hand-truck position.

DETAILED DESCRIPTION

A load carrier 10 in accordance with the present disclosure includes arolling base 12, a pivotable base pusher 14, and a load-carrier modechanger 16 as shown in FIGS. 1A-1C. Load-carrier mode changer 16 can beoperated in the field without tools by a user in a manner suggesteddiagrammatically in FIGS. 4A-4D and illustratively in FIGS. 5-7 and12-14 to convert load carrier 10 from the flat storage mode shown inFIGS. 1A, 4A, and 5 to a front-and-rear-wheel cart mode shown in FIGS.1B, 4C, and 7, and to a 2-wheel hand-truck mode shown in FIGS. 1C, 4D,and 12.

Rolling base 12 includes a load-support frame 18, a left front wheelunit 36 including a left front wheel 21, and a right front wheel unit 38including a right front wheel 22 as shown, for example, in FIGS. 2 and3. Load-support frame 18 includes a left wheel-support rail 31, a rightwheel-support rail 32, and a toe-plate shelf 24 mounted on forward endsof rails 31, 32 for pivotable movement about a shelf pivot axis 24Abetween an inactive flat position shown in FIGS. 1A and 1B used in theflat storage mode and the front-and-rear-wheel cart mode of load carrier10 and an active extended position shown in FIG. 1C and used in the2-wheel hand-truck mode of load carrier 10. Once left front wheel unit36 is mounted on left rail 31, left front wheel unit 36 is pivotableabout a left pivot axis 36A aligned with left rail 31 as suggested inFIG. 3. Once right front wheel unit 38 is mounted on right rail 32,right front wheel unit 38 is pivotable about a right pivot axis 38Aaligned with right rail 32 as suggested in FIG. 3. Load-support frame 18also includes a left end cap 33 to be mounted on a forward end of leftrail 31 after left front wheel unit 36 is mounted on left rail 31 and aright end cap 34 to be mounted on a forward end of right rail 32 afterright front wheel unit 38 is mounted on right rail 32.

Base pusher 14 includes a push handle 55 and an outrigger wheel unit 60configured to be coupled to push handle 55 to move therewith assuggested, for example, in FIGS. 2 and 3. Push handle 55 includes a leftleg 55L, a right leg 55R, and a U-shaped handgrip 55H interconnectingupper ends of legs 55L, 55R as suggested in FIG. 2. Outrigger wheel unit60 includes a left caster 61 including a left rear wheel 61R, a rightcaster 62 including a right rear wheel 62R, and a caster-support rail 64coupled to lower ends of left and right legs 55L, 55R of base pusher 14and to each caster 61, 62.

Mode changer 16 includes a front linkage 70 and a rear linkage 72 assuggested in FIGS. 2 and 3. Front linkage 70 includes a spreader driver80 and a wheel spreader 74 including a pivotable spreader plate 74P andwheel links 75, 76 interposed between and coupled to pivotable spreaderplate 74P and spreader driver 80 as suggested in FIGS. 2 and 3. Frontlinkage 70 also includes a spreader-driver retainer 82 that isconfigured to block or allow sliding movement of spreader driver 80along rails 31, 32 of load-support frame 18 at the option of a user.Rear linkage 72 includes a pivotable pusher rotator 86 and a push rod86P including pusher links 113, 114 pivotably coupled at one end topivotable pusher rotator 86 and at opposite ends to pivotable basepusher 14 at the lower ends of left and right legs 55L, 55R of pushhandle 55 below the caster-support rail 64 as suggested in FIG. 3.Pusher rotator 86 includes a movable handgrip 117 comprising pivot links111, 112 and a crossbar 116 interconnecting pivot links 111, 112 and ahandgrip-motion blocker 118 associated with crossbar 116 as suggested inFIGS. 2 and 3.

In illustrative embodiments, the mode changer 16 is operable in thefield by a user without tools to convert load carrier 16 easily from itsflat storage mode to a front-and-rear-wheel cart mode or an upright2-wheel hand-truck mode. In the flat storage mode, front wheels 20, 21are aligned to cause their treads to face toward one another and theiraxes of rotation to lie in spaced-apart parallel relation to oneanother. In the other modes, front wheels 21, 22 are aligned to causetheir treads to engage and roll on ground 35 underlying rolling base 12and to cause front wheels 21, 22 to rotate about a common axis ofrotation.

Left front wheel unit 36 includes a cam block 49 arranged to liealongside wheel 21 and engage a portion of spreader plate 74P of wheelspreader 74 of front linkage 70 of mode changer 16 during pivotingmotion of base pusher 14 about base-pusher pivot axis 14 to change themode of load carrier 10 from the flat storage mode to thefront-and-rear-wheel cart mode as suggested diagrammatically in FIGS.4A-4C and illustratively in FIGS. 10 and 11. Similarly, right-frontwheel unit 38 includes a cam block 59 near right wheel 22. Cam block 49includes, in sequence, a ROOT section 491, a CAM section 492, and a LOCKsection 493 and cam block 59 includes, in sequence, a ROOT section 591,a CAM section 592, and a LOCK section 593. Spreader plate 74P of wheelspreader 74 engages or lies adjacent to ROOT sections 491, 591 when loadcarrier 10 is in the flat storage mode as suggested in FIG. 4A. Spreaderplate 74P engages CAM sections 492, 592 during the movement of frontlinkage 70 relative to rolling base 12 that accompanies a change of loadcarrier 10 from the flat storage mode to the front-and-rear-wheel modeas suggested in FIGS. 4B and 4C and FIG. 10. In this circumstance,spreader plate 74P is moved toward front wheels 21, 22 to engage CAMsections 492, 592 and ride thereon in camming relation to move thecompanion front wheel unit 36 or 38 from the folded storage position tothe unfolded rolling position and thus spread the front wheel units 36,38 apart. Lastly, spreader plate 74P of wheel spreader 74 engages LOCKsections 493, 593 (e.g., channels) formed in a hook (41 or 51) includedin cam block (49 or 59) as suggested diagrammatically in FIGS. 4C and 4Dand illustratively in FIG. 11 to retain the front wheel units 36, 38 intheir unfolded rolling positions.

Sliding movement of the load-carrier mode changer 16 on the left andright rails 31, 32 of the rolling base 12 to cause the front wheel units36, 38 to pivot from the folded storage positions to the unfoldedrolling positions in response to pivoting movement of the base pusher 14from the stored position to the upright cart position is showndiagrammatically in FIGS. 4A-4C. Movement of the pivotable pusherrotator 86 included in the rear linkage 72 of the load-carrier modechanger 16 from the FIRST POSITION shown in FIG. 4C to the SECONDPOSITION shown in FIG. 4D causes the base pusher 14 to pivot from theupright cart position suggested in FIG. 4C to the laidback hand-truckposition suggested in FIG. 4D.

As suggested in a diagrammatic view of the load carrier 10 provided inFIG. 4A, load carrier 10 is retained in the compact flat storage mode ofFIG. 1A. Front linkage 70 of the load-carrier mode changer 16 includes aslidable spreader driver 80 coupled to the base pusher 14 via the rearlinkage 72 and mounted for sliding movement on the rails 31, 32 includedin the rolling base 12 and a wheel spreader 74 arranged to interconnectthe slidable spreader driver 80 and the pivotable left and right frontwheel units 36, 38. Spreader plate 74P of wheel spreader 74 is arrangedto engage a ROOT section of each front wheel unit 36, 38. Pivotablebase-pusher rotator 86 included in the rear linkage 70 of theload-carrier mode changer 16 is coupled to the base pusher 14 andmounted for pivoting movement on the slidable spreader driver 80 andarranged to lie in a FIRST POSITION on the slidable spreader driver 80.

FIG. 4B is a diagrammatic view similar to FIG. 4A showing that the leftand right front wheel units 36, 38 have pivoted toward one another indirections 121, 122 through an angle of about 45° owing to engagement ofspreader plate 74P of wheel spreader 74 with the CAM section of eachfront wheel unit 36, 38 in response to pivoting movement of the basepusher 14 away from the rolling base 12 about the base-pusher pivot axis14A to cause sliding movement of the slidable spreader driver 80 on theleft and right rails 31, 32 of the rolling base 12 in a direction towardthe front wheel units 36, 38 and movement of spreader plate 74P of wheelspreader 74 on the CAM section of each front wheel unit 36, 38.

FIG. 4C is a diagrammatic view showing that the front wheel units 36, 38have been pivoted further on the rails 31, 32 to assume the unfoldedrolling positions in response to pivoting movement of the base pusher 14to assume the upright cart position and suggesting that spreader plate74P of wheel spreader 74 has been moved along the CAM section of eachfront wheel unit 36, 38 to engage the LOCK section of each front wheelunit 36, 38 to retain the front wheel units 36, 38 in the unfoldedrolling positions.

FIG. 4D is a diagrammatic view showing that the base pusher 14 has beenpivoted in a rearward direction about the base-pusher pivot axis 14Arelative to the rolling base 12 to assume a laidback hand-truck positionin response to pivoting movement of the pivotable base-pusher rotator 86on the slidable spreader driver 80 from the FIRST POSITION in adirection away from the base-pusher pivot axis 14A and toward the frontwheels 21, 22 to arrive at a SECOND POSITION.

In illustrative embodiments, rolling base 12 comprises a load-supportframe 18 including left and right front-wheel support rails 31, 32arranged to lie in spaced-apart parallel relation to one another, a leftfront wheel unit 36 mounted on the left front-wheel support rail 31 forpivotable movement about a left pivot axis 36A, and a right front wheelunit 38 mounted on the right front-wheel support rail 32 for pivotablemovement about a right pivot axis 30A that is arranged to lie inspaced-apart parallel relation to the left pivot axis 36A as suggestedin FIGS. 3, 4A, and 5-7. Each of the left and right front wheel units36, 38 may pivot about its pivot axis 36A or 38A between a foldedstorage position shown in FIG. 1A and an unfolded rolling position shownin FIGS. 1B and 1C. In the folded storage positions, none of the frontwheels 21, 22 in the left and right front wheel units 36, 38 arearranged to engage and roll on ground 35 underlying the rolling base 12as suggested in FIGS. 1A and 4A. However, in the unfolded rollingpositions, the front wheels 21, 22 are arranged to engage and roll onthe ground 35 underlying the rolling base 12 as suggested in FIGS. 1Band 1C.

Load carrier 10 also includes spring means 46, 56 for normally andyieldably pivoting each front wheel unit 36, 38 about its pivot axis 36Aor 38A to assume the folded storage position in which front wheels 21,22 in the front wheel units 36, 38 disengage ground 35 underlying therolling base 12 and the front wheel 21 in the left front wheel unit 36is arranged to extend toward the front wheel 22 in the right front wheelunit 38 as suggested in FIGS. 4A-4C and 5-7. The spring means 46, 56illustratively includes a left torsion spring 46 coupled to the leftrail 31 and the left front wheel unit 36 and a right torsion spring 36coupled to the right rail 32 and the right-front wheel unit 38.

Base pusher 14 is formed to include left and right rear wheels 61R, 62Rin an illustrative embodiment as suggested in FIGS. 1A-1C, 2, and 3. Itis within the scope of this disclosure to include only one rear wheel inbase pusher 14.

Base pusher 14 is mounted on the left and right front-wheel supportrails 31, 32 of the rolling base 12 for pivotable movement about abase-pusher pivot axis 14A in a first direction from a stored positionarranged to lie alongside the left and right front-wheel support rails31, 32 on top of the rolling base 12 in a flat storage mode of the loadcarrier 10 (see FIG. 1A) first through about a 90° angle away from theleft and right front-wheel support rails 31, 32 to reach an upright cartposition to establish a front-and-rear-wheel cart mode of load carrier10 (see FIG. 1B) in which the two rear wheels 61R, 62R of the basepusher 14 along with two front wheels 21, 22 in the left and right frontwheel units 36, 38 roll on ground 35 underlying the load carrier 10.Then the base pusher 14 can be pivoted about the base-pusher pivot axis14A in the same direction through about another 90° angle to reach alaidback hand-truck position in which only the two front wheels 21, 22in the left and right front wheel units 36, 38 roll on ground 35underlying load carrier 10 to establish a 2-wheel hand-truck mode of theload carrier 10 (see FIG. 1C).

Load carrier 10 includes a load-carrier mode changer 16 coupled to therolling base 12 and to the base pusher 14 as suggested in FIGS. 1A-1C,2, and 3. The load-carrier mode changer 16 is configured to providemeans for pivoting the spring-biased left and right front wheel units36, 38 about their pivot axes 36A or 38A to move relative to the leftand right front-wheel support rails 31, 32 from the folded storagepositions shown in FIGS. 1A, 5, and 5A to assume unfolded rollingpositions shown in FIGS. 1B, 7, and 7A in which the front wheels 21, 22included in the left and right front wheel units 36, 38 are arranged toengage and roll on ground 35 underlying the rolling base 12 and rotateabout a common axis of rotation in response to pivoting movement of thebase pusher 14 relative to the rolling base 12 about the base-pusherpivot axis 14A by a user in the field and cooperate with the rear wheels61R, 62R included in the base pusher 14 to establish thefront-and-rear-wheel cart mode of the load carrier 10.

Load-carrier mode changer 16 includes a front linkage 70 coupled to thepivotable left and right front wheel units 36, 38 and a rear linkage 72coupled to the pivotable base pusher 14 as suggested in FIGS. 2, 3, 4A,and 5. The rear linkage 72 is always joined to the front linkage 72 tocooperate therewith to cause the pivotable left and right front wheelunits 36, 38 to pivot against biasing forces provided by the springmeans 46, 56 from the folded storage positions to the unfolded rollingpositions in response to pivoting movement of the base pusher 14 aboutthe base-pusher pivot axis 14A in a direction away from the front wheelunits 36, 38.

In illustrative embodiments, the front linkage 70 includes a slidablespreader driver 80 mounted for sliding movement on the front-wheelsupport rails 31, 32 of the rolling base 12 and a wheel spreader 74coupled to the spreader driver 80 and to the left and right front wheelunits 36, 38 as suggested diagrammatically in FIG. 4A and illustrativelyin FIGS. 2, 3. The rear linkage 72 includes a pivotable pusher rotator86 mounted for movement on the spreader driver 80 between a FIRSTPOSITION and SECOND POSITION and a push rod 86P comprising pusher links113, 114 coupled to the pivotable pusher rotator 86 and to the pivotablebase pusher 14. Normally, the pivotable pusher rotator 86 is retained inthe FIRST POSITION on the spreader driver 80 to cause the front wheelunits 36, 38 to pivot on the rails 31, 32 from their folded storagepositions to their unfolded rolling positions in response to pivoting ofthe base pusher 14 about the base-pusher pivot axis 144 in a directionaway from the front wheel units 36, 38 so as to convert the load carrier10 from the flat storage mode to the front-and-rear-wheel cart mode. Atthe option of a user, the load carrier 10 is converted from thefront-and-rear-wheel cart mode to the 2-wheel hand-truck mode by movingthe pivotable pusher rotator 86 on the spreader driver 80 from the FIRSTPOSITION to the SECOND POSITION to move the push rod 86P relative to therolling base 12 to pivot the base pusher 14 about the base-pusher pivotaxis 14A through an angle of about 90° from the upright cart position tothe laidback hand-truck position.

Load carrier 10 is convertible by a user in the field without tools toassume a flat storage mode, a cart mode, and a 2-wheel hand-truck modeas shown in FIGS. 1A-1C. In the flat storage mode shown in FIG. 1A, apair of front wheels 21, 22 included in a rolling base 12 are in afolded storage position and a base pusher 14 is in a stored positionextending along a load-support frame 18 of the rolling base 12 so thatload carrier 10 is generally flattened for storage. In the cart modeshown in FIG. 1B, front wheels 21, 22 are moved to an unfolded rollingposition and base pusher 14 is moved to an upright cart positionextending generally perpendicular to load-support frame 18 of rollingbase 12 so that load carrier 10 provides a 2-wheeled hand truck fortransporting goods. In the 2-wheel hand-truck mode shown in FIG. 1C,front wheels 21, 22 remain in the unfolded rolling position and basepusher 14 is moved to a laidback hand-truck position extending generallyparallel to frame 18 of rolling base 12 so that load carrier 10 providesa two-wheeled stand-up dolly for transporting goods.

In the illustrative embodiment, load carrier 10 includes a mode changer16 coupled to rolling base 12 and to base pusher 14 as shown in FIGS.1A-1C. Mode changer 16 provides front-wheel mover means for pivotingfront wheels 21, 22 from the folded storage position to the unfoldedrolling position in response to movement of base pusher 14 from thestored position to the upright cart position as shown in FIGS. 5-7A, 10,and 11. Mode changer 16 provides pusher-retainer means for holding basepusher 14 in either the upright cart position or in the laidbackhand-truck position relative to load-support frame 18 as shown in FIGS.7-8A and 14-17.

Load carrier 10 illustratively includes rolling base 12, base pusher 14coupled to rolling base 12, and load-carrier mode changer 16 as shown,for example, in FIGS. 1A-1C. Rolling base 12 is adapted for supportinggoods to be transported by load carrier 10. Base pusher 14 is coupled toload-support frame 18 included in rolling base 12 near a first end 17 ofload-support frame 18 for movement relative to rolling base 12 about abase-pusher pivot axis 14A and is adapted to provide a grip for a userduring use of load carrier 10. Load-carrier mode changer 16 is coupledto rolling base 12 and to base pusher 14 and facilitates reconfigurationof load carrier 10 between modes by moving front wheels 21, 22 includedin rolling base 12 and by holding base pusher 14 in predeterminedpositions relative to rolling base 12.

Rolling base 12 includes a load-support frame 18 and a toe-plate shelf24 coupled to load-support frame 18 near second end 19 of load-supportframe 18 for movement about a shelf pivot axis 24A. Toe-plate shelf 24moves about shelf pivot axis 24A from an inactive flattened position,shown in FIGS. 7 and 7A, to an active extended position shown in FIGS.12 and 12A.

Load-support frame 18 includes a left rail 31, a right rail 32 spacedapart from and arranged to extend parallel to left rail 31, a left endcap 33 sized to receive and to be coupled to left rail 31, and a rightend cap 34 sized to receive and to be coupled to right rail 32 as shownin FIGS. 2 and 3. Left front wheel 21 is coupled to left rail 31 formovement about left wheel axis 36A which extends along left rail 31.Right front wheel 22 is coupled to right rail 32 for movement aboutright wheel axis 38A which extends along right rail 32 so that rightwheel axis 38A is spaced apart from and arranged to extend parallel toleft wheel axis 36A. Toe-plate shelf 24 is coupled to left and right endcaps 33, 34 of load-support frame 18 for movement about shelf pivot axis24A.

Left front wheel unit 36 is coupled to left rail 31 of load-supportframe 18 and a right front wheel unit 38 is coupled to right rail 32 ofload-support frame 18 as shown in FIG. 4. Left front wheel unit 36includes left front wheel 21 and couples left front wheel 21 to leftrail 31 of load-support frame 18 for movement about left wheel axis 36A.Right front wheel unit 38 includes right front wheel 22 and couplesright front wheel 22 to right rail 32 of load-support frame 18 formovement about right wheel axis 38A. Front wheels 21, 22 move aboutwheel axes 36A, 38A from the folded storage positions, shown in FIGS. 5and 5A, to the unfolded rolling positions shown in FIGS. 7 and 7A.Movement of front wheels 21, 22 is independent of movement of toe-plateshelf 24.

In the folded storage positions, front wheels 21, 22 are arranged toextend inwardly toward one another to cause load carrier 10 to beflattened as shown in FIGS. 1A and 5. More specifically, left frontwheel 21 is arranged to extend from left rail 31 toward right frontwheel 22 and right rail 32 of load-support frame 18 when in the foldedstorage position. Correspondingly, right front wheel 22 is arranged toextend from right rail 32 toward left front wheel 21 and left rail 31 ofload-support frame 18 when in the folded storage position.

In the unfolded rolling position, front wheels 21, 22 are arranged toextend downwardly to engage a floor 35 underlying load carrier 10 asshown in FIGS. 1B, 1C, 7, and 14. More specifically, left front wheel 21and right front wheel 22 are arranged to extend in the same downwarddirection away from load-support frame 18 when in the unfolded rollingposition.

Left front wheel unit 36 includes a brace bracket 42 coupled left rail31, a wheel support 44 coupled to left rail 31 for movement about leftwheel axis 36A, and a left front wheel 21 coupled to wheel support 44 assuggested in FIG. 2. A wheel-bias spring 46 is coupled to left rail 31and to wheel support 44. Wheel support 44 includes a rail receiver 47, afork 48, and a cam block 49 as shown in FIGS. 2 and 3. Wheel-bias spring46 is arranged to extend around a portion of left rail 31 and to engagebrace bracket 42 and wheel support 44 to bias wheel support 44, alongwith left front wheel 21, toward the folded storage position as shown inFIGS. 1A, 5, and 5A.

Wheel support 44 of left front wheel unit 36 is illustratively amonolithic component formed to include a rail receiver 47, a fork 48, acam block 49, and a hook 41 as shown in FIGS. 2 and 3. Rail receiver 47is coupled to left rail 31. Fork 48 is coupled to rail receiver 47 andis configured to support left front wheel 21 for rotation relative towheel support 44. Cam block 49 is coupled to fork 48 and interacts withspreader plate 74P of wheel spreader 74 of front linkage 70 ofload-carrier mode changer 16 when left front wheel 21 is moved from thefolded storage position to the unfolded rolling position. Hook 41extends from cam block 49 and is configured to receive base pusher 14when base pusher 14 is in the stored position as shown in FIGS. 1A and 5so that base pusher 14 is held in place relative to rolling base 12.

Right front wheel unit 38 is similar to left front wheel unit 36 andincludes a brace bracket 52 coupled right rail 32, a wheel support 54coupled to right rail 32 for movement about right wheel axis 38A, and aright front wheel 22 coupled to wheel support 54. A wheel-bias spring 56is coupled to right rail 32 and to wheel support 54. Wheel-bias spring56 is arranged to extend around a portion of right rail 32 and to engagebrace bracket 52 and wheel support 54 to bias wheel support 54, alongwith right front wheel 22, toward the folded storage position as shownin FIGS. 1A, 5, and 5A.

Wheel support 54 of right front wheel unit 38 illustratively is amonolithic component formed to include a rail receiver 57, a fork 58, acam block 59, and a hook 51 as shown in FIGS. 2 and 3. Rail receiver 57is coupled to right rail 32. Fork 58 is coupled to rail receiver 57 andis configured to support right front wheel 22 for rotation relative towheel support 54. Cam block 59 is coupled to fork 58 and interacts withspreader plate 74P of wheel spreader 74 of load-carrier mode changer 16when right front wheel 22 is moved from the folded storage position tothe unfolded rolling position. Hook 51 extends from cam block 59 and isconfigured to receive base pusher 14 when base pusher 14 is in thecollapsed storage position as shown in FIGS. 1A and 5 so that basepusher 14 is held in place relative to rolling base 12.

Base pusher 14 illustratively includes a push handle 55 and an outriggerwheel unit 60 as shown, for example, in FIG. 4. Push handle 55 iscoupled to load-support frame 18 of rolling base 12 for movement aboutbase-pusher pivot axis 14A. Outrigger wheel unit 60 is coupled to pushhandle 55 for movement with push handle 55 about base-pusher pivot axis14A and illustratively includes a left caster 61, a right caster 62, anda caster-support rail 64 arranged to interconnect left caster 61 andright caster 62. Base pusher 14 pivots about base-pusher pivot axis 14Afrom the stored position, shown in FIG. 5, to the upright cart position,shown in FIG. 7, and to the laidback hand-truck position shown in FIG.14.

In the stored position shown in FIGS. 1A and 5, base pusher 14 isarranged to extend along load-support frame 18 of the rolling base 12 tocause load carrier 10 to be generally flattened for storage. Morespecifically, push handle 55 of base pusher 14 is arranged to extendover a portion of load-support frame 18 when base pusher 14 is in thestored position. Outrigger wheel unit 60 is arranged to lie generallyoutward of first end 17 of load-support frame 18 to cause left and rightcasters 61, 62 to lie in a plane defined by load-support frame 18 whenbase pusher 14 is in the stored position as shown in FIG. 5A.

In the upright cart position shown in FIGS. 2 and 7, base pusher 14 isarranged to extend generally perpendicular to load-support frame 18 ofrolling base 12 to cause load carrier 10 to provide a four-wheeled cartfor transporting goods as shown in FIGS. 1B and 7. Push handle 55 isarranged to extend upwardly from load-support frame 18 away from anunderlying floor 35 when base pusher 14 is in the upright cart position.Outrigger wheel unit 60 is arranged to extend downwardly fromload-support frame 18 to cause left and right casters 61, 62 to engagean underlying floor 35 when base pusher 14 is in the upright cartposition.

In the laidback hand-truck position show in FIGS. 1C and 14, base pusher14 is arranged to extend generally parallel to load-support frame 18 ofrolling base 12 to cause load carrier 10 to provide a two-wheeledstand-up dolly for transporting goods as shown in FIGS. 1C and 14. Pushhandle 55 is arranged to extend generally parallel to and away fromfirst end 17 of load-support frame 18 when base pusher 14 is in thelaidback hand-truck position. Outrigger wheel unit 60 is arranged toextend generally parallel to and toward second end 19 of load-supportframe 18 when base pusher 14 is in the laidback hand-truck position.

Load-carrier mode changer 16 illustratively includes a front linkage 70and a rear linkage 72 as shown in FIGS. 2 and 3. Front linkage 70 isconfigured to move front wheels 21, 22 from the folded storage positionto the unfolded rolling position in response to movement of base pusher14 from the stored position to the upright cart position as shown inFIGS. 5-7A, 10, and 11. Rear linkage 72 is configured to hold basepusher 14 in either the upright cart position or in the laidbackhand-truck position relative to load-support frame 18 as shown in FIGS.7-8A and 14-17.

Front linkage 70 illustratively includes a wheel spreader 74 comprisinga spreader plate 74P and wheel links 75, 76, and a slidable spreaderdriver 80 as shown in FIGS. 2 and 3. Spreader plate 74P of wheelspreader 74 is configured to engage cam blocks 49, 59 of left and rightfront wheel units 36, 38 to push units 36, 38 and front wheels 21, 22 inthose units 36, 38 from the folded storage position to the unfoldedrolling position as shown in FIGS. 10 and 11. Spreader plate 74P ofwheel spreader 74 is received in LOCK (channel) sections 493, 593 formedin hooks 41, 51 attached to corresponding front wheels 21, 22 when frontwheels 21, 22 are moved to the unfolded-rolling position to hold thefront wheels 21, 22 in the unfolded-rolling position and to brace thefront wheels 21, 22 during use of the load carrier 10. Wheel links 75,76 are pivotably coupled to spreader plate 74P to pivot relative tospreader plate 74P and to slidable spreader driver 80 to pivot relativeto slidable spreader driver 80. Slidable spreader driver 80 is coupledto load-support frame 18 to slide along load-support frame 18.

Rear linkage 72 includes a spreader-driver retainer 82, pivotable pusherrotator 86, and push rod 86P, as shown, for example, in FIGS. 2 and 3.Slidable spreader driver 80 is coupled to load-support frame 18 to sliderelative to load-support frame 18 and to base pusher 14 through rearlinkage 72. Slidable spreader driver 80 facilitates movement of basepusher 14 from the stored position to the upright cart position as shownin FIGS. 5-7. Spreader-driver retainer 82 is configured to block orallow movement of slidable spreader driver 80 along load-support frame18. Rear linkage 72 is coupled to slidable spreader driver 80 and tobase pusher 14 to interconnect slidable spreader driver 80 and basepusher 14. Rear linkage 72 facilitates movement of base pusher 14relative to slidable spreader driver 80 and load-support frame 18 fromthe upright cart position to the laidback hand-truck position as shownin FIGS. 12-14.

Spreader-driver retainer 82 illustratively includes a left spring pin91, a right spring pin 92, and a pin release 95 as shown in FIGS. 2 and3. Left spring pin 91 is coupled to left rail 31 of load-support frame18 and right spring pin 92 is coupled to right rail 32 of load-supportframe 18. Left and right spring pins 91, 92 extend into correspondingleft and right pin receivers 93, 94 formed in slidable spreader driver80 when base pusher 14 is moved to the upright cart position from thestored position as shown in FIGS. 7, 8, and 8A. When spring pins 91, 92are received in pin receivers 93, 94, slidable spreader driver 80 isblocked from movement along load-support frame 18. Pin release 95 isconfigured to push pins 91, 92 out of pin receivers 93, 94 when a useris ready to move base pusher 14 back from the upright cart position tothe stored position.

Pin release 95 illustratively includes left and right pin pushers 101,102, a button 104, and a bias spring 106 as shown in FIG. 4. Left andright pin pushers 101, 102 are mounted to slidable spreader driver 80 toslide outwardly in response to a user pressing button 104 to cause pins91, 92 to be pushed out of pin receivers 93, 94 formed in slidablespreader driver 80 as shown, for example in FIGS. 8 and 9. Button 104 iscoupled to slidable spreader driver 80 for movement relative to slidablespreader driver 80 from a disengaged position allowing left and rightpin pushers 101, 102 to be moved inwardly by pins 91, 92 to an engagedposition pushing left and right pin pusher 101, 102 outwardly. Biasspring 106 is arranged to lie between slidable spreader driver 80 andbutton 104 to bias button 104 to the disengaged position.

Rear linkage 72 includes slider links 111, 112 and pusher links 113, 114as shown in FIGS. 2 and 3. Slider links 111, 112 are coupled to slidablespreader driver 80 to pivot relative to slidable spreader driver 80.Pusher links 113, 114 are pivotably coupled to both a correspondingslider link 111, 112 and base pusher 14 to pivot relative to both thecorresponding slider link 111, 112 and base pusher 14. Pusher rotator 86of rear linkage 72 moves between a FIRST POSITION when base pusher 14 isin the upright cart position and a SECOND POSITION when base pusher 14is in the laidback hand-truck position. When the pusher rotator 86 is inthe FIRST POSITION, slider links 111, 112 extend from slidable spreaderdriver 80 toward the base pusher 14 as shown in FIG. 12. When the pusherrotator 86 is in the SECOND POSITION, slider links 111, 112 extend fromslidable spreader driver 80 away from the base pusher 14 as shown inFIG. 14.

To move load carrier 10 from flat-storage mode to cart-pusher mode, asshown in FIGS. 5-7, a user pivots base pusher 14 about base-pusher pivotaxis 14A from the stored position to the upright cart position in afirst direction as suggested by arrow 120 in FIG. 7. In response tomovement of base pusher 14, slidable spreader driver 80 is moved alongload-support frame 18 in a forward direction as suggested by arrow 125until spreader-driver retainer 82 blocks further movement of slidablespreader driver 80 along load-support frame 18 as suggested in FIG. 8.Also, in response to movement of base pusher 14, front wheels 21, 22 aremoved about axes 36A, 38A as suggested by arrows 121, 122 to move fromthe folded storage positions to the unfolded rolling positions as shownin FIG. 7. The user may also move toe-plate shelf 24 to the activeextended position from the inactive flat position if it is desired.

To move load carrier 10 from 4-wheel cart mode to 2-wheel hand-truckmode, as shown in FIGS. 12-14, a user moves the pusher rotator 86 fromthe FIRST POSITION to the SECOND POSITION as suggested by arrow 124 inFIG. 16 to cause base pusher 14 to pivot about base-pusher pivot axis14A in the first direction from the upright cart position to thelaidback hand-truck position as suggested by arrow 126 in FIG. 14. Theuser may also move toe-plate shelf 24 to the active extended positionfrom the inactive flat position if not already so moved.

To move load carrier 10 from 2-wheel hand-truck mode to the 4-wheel cartmode, a user moves pusher rotator 86 from the SECOND POSITION to theFIRST POSITION. This movement causes base pusher 14 to pivot aboutpusher axis 14A from the laidback hand-truck position to the uprightcart position.

To move load carrier 10 from the 4-wheel cart mode to the flat storagemode, a user first moves the toe-plate shelf 24 to the flat position ifit was moved to the extended position previously. Next, the user pressesbutton 104 of slider retainer 82 as suggested by arrow 130 in FIG. 9. Inresponse to the user pressing button 104, pin pushers 101, 102 are movedoutward and push spring pins 91, 92 out of slidable spreader driver 80to free slidable spreader driver 80 to move along load-support frame 18.The user then pivots base pusher 14 about base-pusher pivot axis 14Afrom the upright cart position to the stored position. As base pusher 14moves from the upright cart position to the stored position, front-wheelmover 70 allows wheel-bias springs 46, 56 to move front wheels 21, 22from the unfolded rolling positions to the folded storage positions.

Another illustrative load carrier 210 is shown in FIGS. 18 and 18A. Theload carrier 210 is substantially similar to the load carrier 10 shownin FIGS. 1-17 and described herein. Accordingly, similar referencenumbers in the 200/300 series indicate features that are common betweenthe load carrier 210 and the load carrier 10. The description of theload carrier 10 is hereby incorporated by reference to apply to the handtruck 210, except in instances when it conflicts with the specificdescription and drawings of the hand truck 210.

Unlike load carrier 10, load carrier 210 includes a pusher rotator 286having forward and aft locks 318, 319 (rather than a single lock 118).Pusher rotator 286 provides means for blocking or allowing movement ofthe links 213, 214 between a first position, corresponding to theupright cart position of the base pusher 214, and a second position,corresponding to the laidback hand-truck position of the base pusher214.

Pusher rotator 286 illustratively includes a handle 315, a crossbar 316,forward lock 318, and aft lock 319 as shown in FIGS. 18 and 18A. Handle315 and crossbar 316 extend between and interconnect slider links 311,312. Forward lock 318 is coupled to slidable spreader driver 280 along aside of slidable spreader driver 280 facing base pusher 214. Aft lock319 is coupled to slidable spreader driver 280 along another side ofslidable spreader driver 280 facing toe-plate shelf 224. Forward lock318 is configured to engage handle 315 when links 213, 214 are in afirst position. Aft lock 319 is configured to engage handle 315 whenshifter linkage 278 is in a second position.

Each lock 318, 319 includes a corresponding wall 338, 339 and acorresponding blocker 348, 349 as shown, for example, in FIG. 18A.Handle 315 is received between a wall 338, 339 and a blocker 348, 349when handle 315 is engaged by a lock 318, 319. Blockers 348, 349 pivotrelative to slidable spreader driver 280 to block or allow movement ofhandle 315 and, in turn, movement of links 213, 214. Blockers 348, 349are biased toward blocking movement of handle 315 and links 213, 214 bya bias spring (not shown).

The invention claimed is:
 1. A collapsible load carrier comprising arolling base including a load-support frame, a left front wheel unitmounted for pivotable movement on the load-support frame about a leftpivot axis between a folded storage position and an unfolded rollingposition, a right front wheel unit mounted for pivotable movement on theload-support frame about a right pivot axis between a folded storageposition and an unfolded rolling position, and a spring yieldablypivoting each front wheel unit about its pivot axis normally to assumethe folded storage position, the folded storage position associated witha flat storage mode of the load carrier in which front wheels in thefront wheel units disengage ground underlying the rolling base and afront wheel in the left front wheel unit is arranged to extend toward afront wheel in the right front wheel unit, and the unfolded rollingposition associated with a front-and-rear-wheel cart mode of the loadcarrier in which the front wheels in the front wheel units are arrangedto engage and roll on ground underlying the rolling base and rotateabout a common axis of rotation, a base pusher mounted for pivotablemovement relative to the load-support frame of the rolling base about abase-pusher pivot axis from a stored position arranged to lie alongsideand on top of the load-support frame of the rolling base toward a2-wheel hand-truck position to lie in generally coplanar relation to theload-support frame of the rolling base to define an included angle ofabout 180° therebetween, and load-carrier mode changer means forpivoting the left and right front wheel units about their pivot axes tomove relative to the load-support frame of the rolling base from thefolded storage position to the unfolded rolling position to cause frontwheels included in the front wheel units to engage and roll on groundunderlying the rolling base in response to pivoting movement of the basepusher relative to the load-support frame about the base-pusher pivotaxis from the stored position on top of the load-support frame towardthe 2-wheel hand-truck position to cause the rear wheel included in thebase pusher to engage and roll on ground underlying the rolling base toestablish a 2-wheel hand-truck mode of the load carrier.
 2. The loadcarrier of claim 1, wherein the left front wheel unit includes a wheelsupport formed to include a cam block and a left front wheel, the rightfront wheel unit includes a wheel support formed to include a cam blockand a right front wheel, and the load carrier mode changer meansincludes a spreader plate configured to engage cam blocks of the leftfront wheel unit and the right front wheel unit to move the left frontwheel unit and the right front wheel unit toward the unfolded rollingposition in response to movement of the base pusher away from the storedposition toward the 2-wheel hand-truck position.
 3. The load carrier ofclaim 2, wherein the spreader plate of the load carrier mode changer iscoupled to the load support frame of the rolling base to pivot relativeto the load support frame of the rolling base in response to movement ofthe base pusher away from the stored position toward the 2-wheelhand-truck position.
 4. The load carrier of claim 1, wherein theload-carrier mode changer means includes a front linkage coupled to theleft and right front wheel units and a rear linkage coupled to the basepusher and mounted for movement relative to the front linkage between afirst position on the front linkage associated with the flat storagemode and the front-and-rear-wheel cart mode of the load carrier and asecond position located on the front linkage between the first positionand the front wheel units and associated with the 2-wheel hand-truckmode of the load carrier.
 5. The load carrier of claim 4, wherein thefront linkage includes a slidable spreader driver mounted for slidingmovement on the load-support frame and a wheel spreader coupled to theslidable spreader driver and arranged to engage a cam provided on eachof the left and right front wheel units to move the left and right frontwheel units against motion-resisting forces applied to the left andright front wheel units by the spring from the folded storage positionstoward the unfolded rolling positions in response to movement of thebase pusher about the base-pusher pivot axis away from the storedposition toward the 2-wheel hand-truck position to move, in unison, therear linkage, the slidable spreader driver, and the wheel spreader as aunit toward the front wheels so that the left and right front wheelunits are spread apart to cause the front wheels in the left and rightfront wheel units to rotate about a common axis and on ground underlyingthe rolling base.
 6. The load carrier of claim 1, wherein theload-carrier mode changer means includes a slidable spreader drivermounted for sliding movement on the load-support frame and a wheelspreader coupled to the spreader driver and arranged to engage a camprovided on each of the left and front wheel units and wherein the leftand right front wheel units move from the folded storage positions tothe unfolded rolling positions during camming engagement with the wheelspreader in response to sliding motion of the slidable spreader driveron the load-support frame toward the front wheels to cause the wheelspreader to move away from the base-pusher pivot axis.
 7. The loadcarrier of claim 6, wherein the wheel spreader includes a proximalportion mounted on the load-support frame for pivotable movement about aspreader-pivot axis and a free portion arranged to pivot about thespreader-pivot axis and engage the cam provided on each of the left andright front wheel units.
 8. The load carrier of claim 6, wherein thewheel spreader includes a spreader plate mounted for pivotable movementon the rolling base and a wheel link pivotably coupled to each of thespreader plate and the slidable spreader driver to convert slidingmotion of the slidable spreader driver into pivoting motion of spreaderplate and wherein the pivoting spreader plate applies a pivot-inducingforce to cams included in the left and right front wheel units to pivotthe left and right front wheel units from the folded storage positionsto the unfolded rolling positions in response to pivoting movement ofthe base pusher in the first direction about the base-pusher pivot axisto change the load carrier from the flat storage mode to thefront-and-rear-wheel cart mode.
 9. The load carrier of claim 1, whereinthe load-carrier mode changer includes a front linkage coupled to theleft and right front wheel units and a rear linkage coupled to the basepusher and mounted for movement on the front linkage between a firstposition associated with the flat storage mode and thefront-and-rear-wheel cart mode of the load carrier and a second positionassociated with a 2-wheel hand-truck mode of the load carrier, the frontand rear linkages cooperate to provide means for pivoting the left andright front wheel units from the folded storage positions to theunfolded rolling positions only when the rear linkage occupies the firstposition on the front linkage, and the base pusher is arranged to pivotabout the base-pusher pivot axis in a direction away from the frontwheel units to move relative to the load-support frame of the rollingbase from the upright cart position to a laidback hand-truck position toestablish a 2-wheel hand-truck mode of the load carrier in response tomovement of the rear linkage relative to the front linkage from thefirst position to the second position.
 10. The load carrier of claim 9,wherein the front linkage includes a slidable spreader driver mountedfor sliding movement on the load-support frame and a wheel spreadercoupled to the slidable spreader driver and arranged to lie in cammingengagement with the left and right front wheel units.
 11. The loadcarrier of claim 10, wherein the wheel spreader includes a spreaderplate mounted for pivotable movement on the rolling base and a wheellink pivotably coupled to each of the spreader plate and the slidablespreader driver to convert sliding motion of the slidable spreaderdriver into pivoting motion of spreader plate and wherein the pivotingspreader plate applies a pivot-inducing force to cams included in theleft and right front wheel units to pivot the left and right front wheelunits from the folded storage positions to the unfolded rollingpositions in response to pivoting movement of the base pusher in thefirst direction about the base-pusher pivot axis.
 12. The load carrierof claim 8, wherein the load-support frame and the base pusher cooperateto define therebetween an included angle of about 180° upon movement ofthe base pusher to the laidback hand-truck position.
 13. A collapsibleload carrier comprising a rolling base including a load-support frame, aleft front wheel unit mounted for pivotable movement on the load-supportframe about a left pivot axis between a folded storage position and anunfolded rolling position, a right front wheel unit mounted forpivotable movement on the load-support frame about a right pivot axisbetween a folded storage position and an unfolded rolling position, anda spring yieldably pivoting each front wheel unit about its pivot axisnormally to assume the folded storage position, the folded storageposition associated with a flat storage mode of the load carrier inwhich front wheels in the front wheel units disengage ground underlyingthe rolling base and a front wheel in the left front wheel unit isarranged to extend toward a front wheel in the right front wheel unit,and the unfolded rolling position associated with a front-and-rear-wheelcart mode of the load carrier in which the front wheels in the frontwheel units are arranged to engage and roll on ground underlying therolling base and rotate about a common axis of rotation, a base pushermounted for pivotable movement relative to the load-support frame of therolling base about a base-pusher pivot axis from a stored positionarranged to lie alongside and on top of the load-support frame of therolling base and associated with the flat storage mode of the loadcarrier in a first direction toward a laidback hand-truck position tocause a rear wheel included in the base pusher to engage and roll onground underlying the rolling base, and a load-carrier mode changerincluding a front linkage mounted for sliding movement on theload-support frame and arranged to engage each of the front wheel unitsin camming relation and a rear linkage coupled to each of the frontlinkage and the base pusher and arranged to cooperate with the frontlinkage to apply a camming force to each of the front wheel units inresponse to pivoting movement of the base pusher about the base-pusherpivot axis in the first direction.
 14. The load carrier of claim 13,wherein the front linkage includes a slidable spreader driver mountedfor sliding movement on the load-support frame and a wheel spreadercoupled to the slidable spreader driver to lie between the slidablespreader driver and the front wheels and arranged to lie in cammingengagement with the front wheel units.
 15. The load carrier of claim 14,wherein the wheel spreader includes a spreader plate mounted forpivotable movement on the rolling base and a wheel link pivotablycoupled to each of the spreader plate and the slidable spreader driverto convert sliding motion of the slidable spreader driver into pivotingmotion of spreader plate and wherein the pivoting spreader plate appliesa pivot-inducing force to cams included in the left and right frontwheel units to pivot the left and right front wheel units from thefolded storage positions to the unfolded rolling positions in responseto pivoting movement of the base pusher in the first direction about thebase-pusher pivot axis.
 16. The load carrier of claim 14, wherein therear linkage is mounted for movement on the front linkage between afirst position associated with the flat storage mode and thefront-and-rear-wheel cart mode of the load carrier and a second positionassociated with the 2-wheel hand-truck mode of the load carrier.
 17. Theload carrier of claim 13, wherein the load-support frame and the basepusher cooperate to define therebetween an included angle of about 180°upon movement of the base pusher to the laidback hand-truck position.18. A collapsible load carrier comprising a rolling base including aload-support frame, a left front wheel unit mounted for pivotablemovement on the load-support frame about a left pivot axis between afolded storage position and an unfolded rolling position, a right frontwheel unit mounted for pivotable movement on the load-support frameabout a right pivot axis between a folded storage position and anunfolded rolling position, and a spring yieldably pivoting each frontwheel unit about its pivot axis normally to assume the folded storageposition, the folded storage position associated with a flat storagemode of the load carrier in which front wheels in the front wheel unitsdisengage ground underlying the rolling base and a front wheel in theleft front wheel unit is arranged to extend toward a front wheel in theright front wheel unit, and the unfolded rolling position associatedwith a front-and-rear-wheel cart mode of the load carrier in which thefront wheels in the front wheel units are arranged to engage and roll onground underlying the rolling base and rotate about a common axis ofrotation, a base pusher mounted for pivotable movement relative to theload-support frame of the rolling base about a base-pusher pivot axisfrom a stored position arranged to lie alongside and on top of theload-support frame of the rolling base and associated with the flatstorage mode of the load carrier in a first direction toward a laidbackhand-truck position to cause a rear wheel included in the base pusher toengage and roll on ground underlying the rolling base, and a spreaderplate mounted for pivotable movement on the rolling base, the spreaderplate configured to apply a pivot-inducing force to cams included in theleft and right front wheel units to pivot the left and right front wheelunits from the folded storage positions to the unfolded rollingpositions in response to pivoting movement of the base pusher in thefirst direction about the base-pusher pivot axis.
 19. The collapsibleload carrier of claim 18, further comprising a slidable spreader drivermounted for sliding movement on the load-support frame and a wheel linkpivotably coupled to each of the spreader plate and the slidablespreader driver to convert sliding motion of the slidable spreaderdriver into pivoting motion of spreader plate.
 20. The collapsible loadcarrier of claim 18, further comprising a pusher link pivotably coupledto the base pusher at a first end and coupled to the slidable spreaderfor movement therewith along the load-support frame at a second end.